PROJECTSUMMARY/ABSTRACT Theevolutionofproteinsunderpinsawiderangeoffundamentallyimportantbiological processes,includingtheadaptationofvirusesthatarerelevanttohumanhealth.Overthelast fewdecades,acombinationofexperimentalandobservationalapproacheshasprovidedagreat dealofqualitativeunderstandingintoproteinevolution.Thegoaloftheproposedresearchisto usethisunderstandingtoguidetheconstructionofquantitativemodelsofproteinevolutionthat areinformedbyexperiments.Suchmodelsareessentialtoleverageburgeoningnewsourcesof experimentaldataonproteinandvirusevolution.Theproposedresearchcentersonfour interconnectedgoals:(1)Quantifytheextentthatexperimentalmeasurementsoftheeffectsof singleanddoublemutationscanbegeneralizedtoanevolutionarilyrelevantspanofprotein homologsorviralstrains.(2)Developstatisticaltechniquestoassesstheadequacyof experimentsfordescribingactualnaturalselection,includingwhentheseexperimentsmeasure epistaticinteractions.(3)Devisehigh-??throughputexperimentstoidentifymutationsthatenable influenzavirustoadapttonewhosts,andusetheresultingmeasurementstoscorethe pandemicriskposedbyviralstrains.(4)Relatetheevolutionofinfluenzaviruswithinsingle infectedhumanstotheconstraintsandselectiononthevirus?slong-??termevolutionataglobal scale.Allfourofthesegoalsleveragenewtypesofdatatoinformbetteranalysesofevolutionin nature.Theresultinginsightsandmethodswilladvancebasicevolutionarybiology,andwillbe directlyrelevanttothestudyofbiomedicallyimportantvirusessuchasinfluenza.